Detection of CO2 leaks from carbon capture and storage sites with combined atmospheric CO2 and O2 measurements.

This paper presents a transportable instrument that simultaneously measures the CO 2 and (relative) O 2 concentration of the atmosphere with the purpose to aid in the detection of CO 2 leaks from CCS sites. CO 2 and O 2 are coupled in most processes on earth (e.g., photosynthesis, respiration and fossil fuel burning), but not in the case of a leak from a CCS site. Whereas a natural increase of the CO 2 concentration is accompanied by a drop in the O 2 concentration, an increase in the CO 2 concentration caused by a leak from a CCS site does not have any effect on the O 2 concentration. The transportable instrument we present here shows an excellent precision for the CO 2 measurements; for O 2 the transportable and flexible design of our system compromised the precision somewhat. The precision in both CO 2 and O 2 determines the detection limit of the system for leaks of CO 2 . The principle of CO 2 leak detection is illustrated by several CO 2 release experiments in which CO 2 was released at a small distance from the air inlet of the measurement system. We present two strategies that can be used to analyze a dataset to find a leak of CO 2 . The detection limit of our instrument is estimated to be around 6 ppm. If a transportable design would not be necessary, the precision for the O 2 measurements can be improved such that the ultimate detection limit of this method is estimated to be around 3 ppm, which would correspond to distances up to 500 m for a leak of 1000 ton CO 2 year −1 (32 g s −1 ) provided favorable atmospheric conditions (wind direction and atmospheric stability) exist. This implies that monitoring time should be long enough to ensure that these conditions occur. [ABSTRACT FROM AUTHOR]